JOURNAL OF FOOD RESEARCH (UNIVERSITY OF TABRIZ)
Year:2013 | Volume:23 | Issue:1|Papers Count:12

In this research, the effect of variable cheese making factors on rennet coagulation kinetic was studied. Three coagulation parameters-lag time, coagulation rate and inflexion time (time for reaching the point of maximum coagulation rate) were evaluated as a function rennet content (0.01–0.03 g/kg), whey protein powder (0.7–2.8 %) and renneting temperature (25–45 oC) using a response surface methodology. Data analysis showed that with a decrease in whey protein concentration or with an increase in rennet content and renneting temperature, coagulation rate increased while the lag time and time at inflection point decreased. The optimum conditions of milk coagulation were: rennet content, 0.025 g/kg of milk; whey protein powder, 0.93%; and renneting temperature, 44.9 oC. Under such conditions, the predicted coagulation rate, lag time and time at inflection point were 0.0092 min-1, 1.009 min and 1.79 min, respectively.

For determining the rationale of reducing rice grain strength during harvesting and post-harvesting and measuring the quality of grains, it is necessary to use the proper method and device, especially in bulk samples. One of this quality index is grain breakage susceptibility index (BSI). For determining this index it is possible to use a centrifugal impact tester and calculate the BSI in weight percent. Accordingly, after modifying a laboratory milling device, the effect of type of blade, blade rotating speed, time of milling and grain moisture content were investigated on the rate of grain breakage in an experimental design and in the form of a factorial test by conducting 108 milling tests. The results of the tests showed that all of independent factors had a statistical significant effect on BSI. The minimum value of BSI equal to 3.5%, was related to minimum rate of rotational velocity, minimum rate of milling time and minimum value of moisture content using flat blade, while the maximum value of BSI was equal to 96.8%. Based on the results of this research, it seems that by conducting more experiments in a wider range of milling time and rotational velocity in common varieties, it will be possible to achieve a reliable method for determining the rice quality in bulk samples according to its breakage susceptibility index.

Although food and beverage industry is considered as one of the relative merits of entering into international trade, because location and climate of Iran' s, but this industry has not been able to commensurate its worthy position in the world. Among the reason presented for this condition, the inability of active firms in this industry to produce with their full capacity is of great importance. Accordingly, the issue of optimal size especially for new firms awareness as well as the production capacities released is of the key issues explored in this industry and the investigation of its changes, makes up the main purpose of this paper. For this purpose, Comanor–Wilson index has been used. In addition, data is collected from the Statistical Center of Iran on early years of second, third and fourth development plans. The results of this paper indicate that the optimal size of the food and beverage industry based on both current and constant prices has shown an upward trend. In addition, in each study period more than 90 percent of firms in this industry are active in less than the amount of optimum size.

Oat contains considerable amount of  b-glucan and hence is known as a functional cereal. b-glucan is a fiber that has positive effects on human health. On the other hand, the average consumption of fiber is lower than recommended values. Accordingly, diseases such as coronary and heart disease as well as obesity are increasing. The main aim of this study was to increase the fiber content of biscuits as a favorite food of low fiber content. Therefore, the effects of replacement of oat bran (as a rich source of fiber) at different levels (0, 5, 10, 15 and 20%) with wheat flour on the characteristics of the dough and biscuit was studied. The results showed that the Young modulus of the dough increased, while springiness and adhesiveness decreased. In addition, the biscuits became harder and the force required to break the biscuits decreased. Determination of the biscuits color showed that the darkness, redness and yellowness of the samples increased with increasing the quantity of the bran. Based on the sensory evaluation results, inclusion of more than 15% bran had significant undesirable effects on the quality attributes of the samples. Overall, inclusion of maximum 15% of oat bran in production of biscuit was suggested.

Pasta products are known in all countries, per capita consumption of these products has increased in recent years in Iran. The importance of these products requires suitable methods for the evaluation of their quality. In this study, sensory evaluation, Hunter lap, Minolta and image analysis were used for the color measurement of pasts products, which reflects their overall quality. Results showed that the fitted model for sensory evaluation and image analysis methods gave high accuracy. However, these models had not suitable accuracy in Hunter lap and Minolta. Also evaluation of the correlation between different indices of image analysis methods showed that saturation has good correlation with sensory and yellow index from Minolta and Hunter methods. Therefore, it can be used to predict the yellowness of pasta with a high confidence.

Soy protein isolate (SPI) is the most refined form of soy protein products which has been used for its desirable nutritional and functional properties. SPIs produced from three different soy flours with various levels of protein dispersibility indexes (PDI) and residual fat (RF) contents including defatted soy flour (PDI 55.10, RF 3.67), low fat soy flour (PDI 32.71, RF 14.34) and full fat soy flour (PDI 28.72, RF 22.08) were investigated for yield, chemical properties and key protein functional properties. Lower PDI values and higher RF contents of the starting materials could be resulted in lower amounts of SPI yield and protein yield. Although the presence of higher RF in soy flours produced SPIs with higher fat contents, but it reduced protein contents. Since the PDI values of the final products were similar, the amounts of water holding capacity, fat binding capacity, foaming capacity and stability, and emulsifying properties were affected negatively by the amounts of SPI fat content.

Bene hull (Pistacia atlantica) contains noticeable antioxidant components. The aim of this study was to obtain a set of optimum conditions for bioactive compounds extraction process from bene hull using subcritical water by response surface methodology (RSM). Temperature (110 – 200 oC), processing time (30-60 minutes) and water to bene hull ratio (10: 1-50: 1) were the factors investigated. Experimental design was performed using central composite face centered design (CCFD) and RSM. The optimal conditions for maximizing antioxidant activity were at 196.81 oC for 52.57 min and the ratio of 43.61: 1 for water to bene hull. Under these conditions, the amount of polyphenolic compounds, reduction power according to EC50 and DPPH free radical scavenging activity according to EC50 were predicted to be 2284 mg gallic acid / 100 g bene hull, 0.2002 mg /ml and 0.6284 mg/ ml, respectively. Extraction and analysis of extracts in optimal point support these results.

Bread is a perishable product which is best consumed when it is fresh. The loss of freshness is due to the microbial spoilage and complex processes known as staling. Sourdough is characterized by a complex microbial ecosystem, mainly represented by lactic acid bacteria and yeasts. The aim of this study was to investigate the application of L. plantarum, L. reuteri and their combination in sourdough preparation. In this study, control breads showed higher pH (5.63), lower TTA, higher loaf volume and height than those prepared from sourdough. Results showed that sourdough bread prepared by L. reuteri received better sensory scores, had lower staling rate and higher shelf-life than those prepared from L. plantarum.

Fat replacement with oat bran derivative in certain bakery products provides the possibility to create high-quality products. The objective of the present study was to produce reduced-fat shortened cakes containing oat bran derivative with suitable quality regarding desirable sensory properties, pH, hardness, and specific volume. Effect of shortening replacement with oat bran derivative named Nutrim oat bran, 20% and 40% by weight, on the aforesaid properties of shortened cakes was examined. pH, hardness and specific volume of the cakes were measured using electronic pH meter, Testometric and rapeseed displacement method, respectively. Regarding sensory properties, samples were evaluated using trained panelists (n=9) via hedonic scaling and overall acceptance tests. A completely randomized experimental design was used in the present study and the comparison of means was made by the Duncan's multiple range test at a=1%. This replacement did not show any significant effect on the pH of cakes and a significant increase in hardness and a significant decrease in specific volume were noted in the 40% treatment sample, compared to, both, the control and the 20% treatment samples. No significant difference in all sensory attributes was detected among the samples. Furthermore, the acceptance rating for the category of overall acceptability has been similar for all samples. The treatment samples had suitable pH and sensory quality. However, the preferred sample was the 20% treatment sample for its proper hardness and specific volume.

In order to study of the fruit quality and antioxidant attributes of interspecific hybrid and its comparison with some plum and apricot cultivars, an experiment was conducted as a complete randomized design with 4 apricot, 2 plum cultivars and an interspecific plum-apricot hybrid in three replicate. Fruit were harvested at physiological ripening stage and fruit firmness, total acidity, pH, total soluble solids content, ascorbic acid, total phenol and flavonoids and antioxidant capacity were evaluated. Results showed that 'Shablon' plum have the highest fruit flesh firmness. The highest and the lowest total soluble solid content were recorded in 'Nasiri' and 'Dorosht-Malayer' cultivars, respectively. 'Ghorban-Maraghe' and the interspecific hybrid, showed the highest and lowest vitamin C content, respectively. The highest phenol content was recorded in 'Shablon' plum. Generally, the phenol content of plums and the interspecific hybrid were higher than apricots. Among the plums, apricots and interspecific hybrid no significant difference was recorded on the total flavonoid content. The antioxidant capacity of plums was higher than apricots, while hybrid showed intermediate values with respect to the values observed in the parents.

Iran is one of the largest pistachio producer and exporter in the world. Under unfavorable conditions during storage, pistachio quality will be reduced due to undesirable reactions. This study was conducted to evaluate the influence of chitosan coating with different molecular weights and concentrations on oxidation activity in the Akbary variety of pistachio nuts. Therefore, using acetic acid as 1% (v/v), chitosan with low molecular weight (LMC) and medium molecular weights (MMC) at concentrations of 0.5%, 1% and 1.5% V/W were prepared and pistachios were coated by them. In order to prepare control group, coating was performed with water and acetic acid as 1% V/V. Coated pistachios were packed in polyethylene bags and kept at room temperature and relative humidity (25-27 oC and 35-45%) for six months. Samples were examined every two weeks for peroxide and thiobarbituric acid value during storage. The results showed that during storage, chitosan coating reduced the rate of oxidation significantly (P<0.05). The LMC exhibited higher anti- oxidant activity than MMC and increased concentration correlated with higher antioxidant activity. The thiobarbituric acid value of pistachios was always zero due to non-formation of secondary compounds of oxidation reactions. In this research, LMC was found appropriate edible coating material for pistachio nuts.

The effect of addition of maltodextrin on physicochemical and microstructure of non-fat yogurt was studied. Non-fat yoghurt was prepared from reconstitute skimmed milk powder. Maltodextrin was added to reconstitute skimmed milk powder with 14% total solids (w/w) at three levels (0 (control sample), 1, 2, and 3%). The mixtures were inoculated using a DVS yogurt starter culture and the obtained yogurt samples stored at 5oC. Physicochemical properties of the yogurt samples such as pH, acidity, total solids, syneresis, textural properties, color and microstructure were studied after one day storage. Increasing the amount of maltodextrin did not have any significant effect on pH and titratable acidity of samples, but increased the total solids of samples, in proportion to added maltodextrin. Addition of maltodextrin led to the decrease in susceptibility to syneresis, but yogurt containing 1% maltodextrin had more syneresis than the control. Increasing 2 and 3% of maltodextrin led to more compact and homogeneity microstructure. However, the yogurt containing 1% maltodextrin had less compact than the control and was more porous in scanning electron microscopy. The yogurt containing 3% maltodextrin and control sample had the highest and lowest firmness, respectively. Maltodextrin had no significant effect on adhesiveness and gumminess, but decreased the cohesiveness of yogurt samples. The color parameters (L*, a* and b*) of yogurt samples did not show any significant differences. In view of compact microstructure, low syneresis and high firmness, maltodextrin at 3% level can be used as a suitable fat replacer to develop a formulation of non-fat set type yogurt.